A method of manufacturing a non-volatile semiconductor memory cell with a separate tunnel window

 

The invention relates to a method of manufacturing a nonvolatile semiconductor memory cell (SZ) with a single cell (TF) with the tunnel window, and the tunneling region (TG) using cells (TF) with the tunnel window as a mask to perform at a late stage of tunnel implantation (I_T). The technical result of memory cells with little need for the area and a large number of cycles programming/erasing. 2 C.p. f-crystals, 6 ill.

The invention relates to a method of manufacturing a non-volatile semiconductor memory cell with a separate tunnel window and, in particular, to a method of manufacturing the EEPROM cell with a small need for the area and a large number of cycles programming/erasing.

Non-volatile semiconductor memory cell with the ability to re-record gain in circuits with a high degree of integration all the more important because they are, for example, smart cards can store variable data for a long period of time and without the use of power.

Depending on the type of nonvolatile semiconductor memory cells Prince who is basically, from cell TF with the tunnel window and transistor memory cell TZ. According Fig.5, transistor memory cell TZ consists of a relatively thick and impervious to the leakage currents of the layer 3 shutter, located on top of it a layer 5 floating gate, a dielectric layer 6 and layer 7 of the control electrode. Put in layer 5 floating gate charge determines the behavior of the corresponding field-effect transistor in the switching mode, which occurs through the field 1 of the source and drain and layer 7 of the control electrode. To enter charges in layer 5 floating gate memory cell contains the cell TF with the tunnel window, which basically has the same sequence of layers as the transistor memory cell TZ, moreover, however, the insulating layer between the semiconductor substrate 100 and the layer 5 of the floating gate consists of a very thin tunnel layer 4.

When producing normal cells TZ EEPROM first carry out ion implantation in the area of the cell TF with the tunnel window for the formation of homogeneous tunneling region 2'. Then put the tunnel insulating layer 4 or layer 3 of the shutter and the layer 5 floating gate, a dielectric layer 6 and layer 7 driving the kăđẫa cell SZ as a mask, the semiconductor substrate 100 is performed by samoobladanie region 1 of the source and drain. Thus receive only high-quality non-volatile semiconductor memory cell with the possibility of re-recording, which has a very long service life. The lifetime indicates the number of cycles programming/erasing and the conventional EEPROM is typically about 10⁶the loops.

The disadvantage of these conventional EEPROM, however, is a high need in the area for the memory cell SZ, so it finds application in circuits with a high degree of integration only conditionally.

In contrast, memory cells "fast" EPROM have very small need of space. In Fig.6 shows a section normal memory cells "fast" EPROM, and on the semiconductor substrate 100 is applied, the tunneling oxide layer 4, layer 5 floating gate, a dielectric layer 6 and layer 7 of the control electrode. To perform the tunneling region in the area of TF' tunnel window memory cells "fast" EPROM using stablehouse memory cells in the semiconductor substrate 100 is performed by samoobladanie the area of implantation. Then, using a memory cell and an additional auxiliary materials the Noah memory cells "fast" EPROM similarly, as described above EEPROM memory cells in layer 5 of the floating gate in area TF' tunnel window through the tunnel layer 4 is injected charge through, for example, injection of hot charge carriers and/or tunneling through the Fowler-Nordheim. Put this way, the charge carriers then determine the behavior of the zone TZ' transistor cell in the switching mode.

Despite the significantly less need to square this normal memory cells "fast" EPROM, this type of non-volatile memory cells has one major disadvantage in that their service life, i.e. the number of cycles programming/erasing, significantly lower than that of the conventional memory cell EEPROM of Fig.4. As a rule, the life of these storage cells "fast" EPROM is about 10³the loops.

Another disadvantage of these conventional non-volatile memory cells with the possibility of re-recordings is that they can be combined in a common integrated circuit only conditionally. The reason for this is, in particular, the fact that pre-made according to Fig.5 implantation tunnel region 2' affects the thickness of the executed then the tunneling layer 4. More specifically, when primeape thickness, than in the storage cell "fast" EPROM of Fig.6. Next region 2' of the implant of Fig.5 very susceptible to subsequent heat treatment, whereas region 2 of the implant of Fig.6 perform only at a relatively late point in time in the manufacturing process. Due to this, executed in the same integrated circuit memory cell of Fig.4 and 5 having different voltage programming/erasing.

Forth from US 5565371 known method of manufacturing a non-volatile semiconductor memory cell with a separate tunnel window, wherein the programming transistor memory cells is implemented by injection of hot charge carriers, and the erasing transistor memory cells through tunneling, Fowler-Nordheim. The disadvantage, however, is the high demand in the area, as well as many non-standard technological processes. The combination of this method with conventional methods, therefore, impossible.

The basis of the invention lies in the task of creating a method of manufacturing a non-volatile semiconductor memory cell with a separate tunnel window when using standard processes would omens through events p. 1 formula.

In particular, by performing tunneling regions in the active area of the cells with the tunnel window after performing the tunneling layer, you can create a non-volatile semiconductor memory cell, which in respect of its lifetime, i.e., cycles programming/erasing equivalent of a conventional EEPROM cell, however, significantly improved in respect of their needs in the area. In addition, manufactured thus memory cell can easily implement in a common integrated circuit with the normal memory cells "fast" EPROM using standard processes. Working voltage (voltage of the programming, erasing and reading) can be the same as for various forms of non-volatile semiconductor memory cells.

Mostly tunneling region perform with samoobladanie using at least one layer of a cell with a tunnel window through implantation. In particular, schemes with a high degree of integration with structure sizes1 micron memory cells can be made so simply and reliably. Implantation can occur when this vertically and/or nickolaus close to each other so when the application voltage of their zone of space charge perform so-called effect clamping. Thus, under the tunnel layer get very homogeneous tunneling region, which is comparable with previously implanted tunnel area, so when programming/erasing arise uniform field strength and increases service life.

Mostly the connecting area of the floating gate and the connecting area of the control electrode is performed concurrently with the corresponding floating gate layers and layers of the control electrode cell with a tunnel window and transistor memory cells, providing further simplification of the manufacturing process.

In the dependent claims, characterized preferred implementation of the invention.

The invention is described in more detail below using examples with reference to the drawings, which depict: - Fig.1: sectional view of a nonvolatile semiconductor memory cell with a separate tunnel window according to the first exemplary embodiment; - Fig. 2: an enlarged section shown in Fig. 1 cell with a tunnel window according to the second example vypolneniyu incision cell with a tunnel window according to the third exemplary embodiment; - Fig.5: sectional view of a memory cell EEPROM according to the prior art; - Fig. 6: sectional view of a memory cell "fast" EPROM according to the prior art.

In Fig. 1 shows a schematic cross-section of non-volatile semiconductor memory cell with a separate tunnel window according to the first exemplary embodiment. The same reference position indicate the same or similar layers or components, as in Fig.5 and 6, so the detailed description below is missing.

In Fig. 1 on a semiconductor substrate 100 made of a transistor memory cell TZ, cell TF with the tunnel window and the connecting area VB. Transistor memory cell TZ, the connecting area VB and cell TF with the tunnel window are in this case, a memory cell SZ. Mainly the semiconductor substrate 100 is composed of silicon, but it may also contain semiconductor connection And^IIIIn^Vor another semiconductor substrate. The memory cell SZ can be implemented as p-MOS cell, the n-MOS cells or CMOS cell in the semiconductor substrate 100, and the respective pockets p and/or n-type.

In Fig. 1-transistor memory cell TZ consists of insulating the floating gate (poly-si) for accumulating charges. In accordance with the accumulated layer 5 floating gate charges under layer 3 gate channel region KG becomes conductive or non-conductive, resulting in the reading of the memory cells SZ can be read logical information 0 or 1. To control transistor memory cell TZ provides layer 7 of the control electrode, insulated from the layer 5 floating gate dielectric layer 6. Thus held in the layer 5 floating gate charge can flow either in the semiconductor substrate 100 or the layer 7 of the control electrode. At a distance from the transistor memory cell TZ in Fig.1 is cell TF with the tunnel window, through which the connecting zone VB is connected with a transistor memory cell TZ and is used for recording and erasing, for example, by injection of hot charge carriers and/or tunneling through the Fowler-Nordheim.

Cell TF with the tunnel window mainly consists of the same layers as the transistor memory cell TZ, and only the tunneling layer 4 is sufficiently low for tunneling thickness. The tunneling layer 4 consists mainly of a tunnel oxide layer, for example of SiO₂. Lying above it, the layer is the speaker transistor memory cell TZ and through the dielectric layer T6 tunnel window is isolated from the conductive layer T7 control electrode of the tunneling window. The dielectric layer T6 tunnel window is, as the dielectric layer 6, mainly from the sequence IT-layers (oxide/nitride/oxide), and it may also consist, however, of the additional insulating dielectric layer. Conductive layer T7 control electrode of the tunneling window and a conductive layer T5 floating gate tunnel open as layer 7 of the control electrode and the layer 5 of the floating gate, are mostly composed of polysilicon, but may also consist of other conductive and/or accumulating the charge material.

The connecting area VB usually consists of the same sequence of layers as the transistor memory cell TZ or cell TF with the tunnel window, and, in General, the layer 7 of the control electrode is connected through a connecting zone VB7 of the control electrode with a layer of T7 control electrode of the tunneling window, and the layer 5 floating gate through the connecting area VB5 floating gate layer T5 floating gate tunnel open. The connecting area 7 of the control electrode and the connecting zone 5 floating gate can be, however, implemented by metallic conductive paths and/or diffusion region is executed separately from each other transistor memory cell TZ and cell TF with the tunnel window, which can be implemented by a suitable etching and/or photolithography. Cell TF with the tunnel window can be a protrusion, nose or other geometric structure, which is possible mainly bilateral implantation tunnel implantation of I_T.

In Fig.1 in accordance with this tunnel region TG perform through relatively late in the process of manufacturing the tunneling implant I_T, which mainly corresponds to the tunneling implant has simultaneously made of memory cells "fast" EPROM. Due to this can be made as cell TF with the tunnel window of the storage cells SZ, and areas with the tunnel window is made in the same process memory cells "fast" EPROM (not shown). Since the tunneling layer 4 of the memory cell SZ, according to the invention, operates mainly for the same operation as the storage cells "fast" EPROM (not shown), both memory cells have the same properties of the programming/erasing, and the demand for space is reduced and service life is increased.

Below is described a method of manufacturing a nonvolatile semiconductor zapominayusciye zone for cell TF with the tunnel window and transistor memory cell TZ. Formed in this way the groove is filled mostly deposited layer of SiO₂and then planarizing. Similarly for the isolation of active areas, you can apply the LOCOS process.

After that, in the active areas of the transistor memory cell TZ and cell TF with the tunnel window and perform accordingly structure layer 3 gate and the tunneling layer 4. Then put a layer 5 floating gate, a dielectric layer 6 and layer 7 of the control electrode that structure in such a way that occurs is shown in Fig.1 section.

In Fig.1 STI-layers are lying parallel to the depicted cross-section areas of the storage cells SZ (not shown). Similarly the connecting area VB7 the control electrode and the connecting area VB5 floating gate denote the corresponding layers in the (spatial) potabilizaa section plane. To perform cell TF with the tunnel window and transistor memory cell TZ then perform the etching of the layers 3, 5, 6 and 7, or 4, T5, T6 and T7, the result is shown in Fig.1 stabilopozii cell TF and TZ. When implemented then the tunneling implant I_Tnext to stablehouse cell TF with the tunnel window do with self is the first region TG. During the subsequent implantation of source-drain (not shown) between the cell TF with the tunnel window and on both sides of the transistor storage cells SZ perform with samoobladanie region 1 source-drain. The cell TF with the tunnel window can use an auxiliary layer or spacer (not shown).

Area 1 source-drain transistor between the memory cell SZ and cell TF with the tunnel window creates this contact with cell TF with the tunnel window, and transistor memory cell TZ and is used both for reading and for programming/erasing memory cells SZ.

In Fig.2 shows an enlarged section shown in Fig.1 cell TF with the tunnel window on the tunnel stage implantation. In Fig.2 on the semiconductor substrate 100 is stablehorse device of the tunnel layer 4, layer T5 floating gate tunnel window, the dielectric layer T6 tunnel window layer and T7 of the control electrode of the tunneling window. After structuring of this stablehouse cell TF with the tunnel window is the actual tunnel implantation of I_Tfor the formation of the tunneling region TG under the tunnel layer 4. With samoobladanie using the headquarters of analnogo layer 4 underneath, and thus formed homogeneous tunneling region TG.

Such execution regions 2 implantation is possible, in particular, at very small sizes, structures, less than 1 μm, and the scattering effects during implantation is used to perform the matching tunnel areas TG. For implantation of the n-regions are suitable, in particular, As because he has a small depth of penetration and relatively high diffusion. For doping can be used, however, it is also Ph and/or Sb. Similarly to perform the p-regions can be used p-alloying materials, if they have sufficient scattering under the tunnel layer 4 and create due to this fairly homogeneous tunneling region TG.

Alternatively, the vertical tunnel implantation of I_Tyou can also inclined tunnel implantation of I_TSand implantation occurs under the tunnel layer 4 at an angle 5-8^o. Thus, for example, the implantation region 2 is formed in the semiconductor substrate 100 with one hand completely under serving as the mask cell TF with the tunnel window. Thus, under the tunnel layer 4 can also create homogeneous tunneling region TG. Alternatively, the image is to go with multiple parties (two) inclined under the tunnel layer 4.

In Fig. 4 tunnel implantation of I_Tmight happen next, so that formed in the semiconductor substrate 100 corresponding region 2 implantation do not touch each other, and only partially extend under the tunnel layer 4. Region 2 implantation extend, however, under the tunnel layer 4 so that upon application of operating voltage (e.g. voltage programming/erasing, for example, -10 V To +6 V) zone RLZ space charge regions 2 implantation touch each other, resulting in the so-called effect clamping and under the tunnel layer 4 is again formed homogeneous tunneling region. Also in this case, the receive memory cell, characterized by increased service life, i.e. the number of cycles programming/erasing.

According to the invention, the tunneling implant I_Tperform primarily using the whole cell TF with the tunnel window as a mask. However, as a layer mask, you can use only one in the cell with the tunnel window layer or an additional layer mask in the form of photoresist and/or wear-resistant mask. Mainly for tunnel implantation of I_Tyou can use the seat described above sequence of layers you can also use another sequence of layers (for example, SONOX), if due to this, the formation of nonvolatile semiconductor memory cells with the possibility of re-entry.

Claims

1. A method of manufacturing a non-volatile semiconductor memory cell with a separate tunnel window consisting of the following steps: performing cell (TF) with the tunnel window with the tunnel region (TG), the tunneling layer (4), a storage layer (T5) of the tunneling window, a dielectric layer (T6) tunnel window and the layer (T7) of the control electrode of the tunneling window; follow-transistor memory cell TZ) with a channel region (KG), layer (3) of the shutter, the storage layer (5), dielectric layer (6) and a layer (7) the control electrode with run separately from one another transistor memory cell TZ) and cells (TF) with the tunnel window in active regions of a semiconductor substrate (100), and a connecting zone (VB) for connection of the cell (TF) with the tunnel window transistor memory cell (TZ) in the inactive region of a semiconductor substrate (100), while the tunnel doping region (TG) in the active region of the cell (TF) with the tunnel window is carried out after the execution of the tunneling layer (4), if the color under the tunnel layer (4), and when the application voltage zone (RLZ) space charge regions 2 implantation extend completely under the tunneling layer, wherein the tunneling region is performed through a relatively late process of manufacturing the tunneling implant IT, mainly corresponding tunnel implantation for simultaneously fabricated memory cells "fast" EPROM, which can be performed as cell TF with the tunnel window of the storage cells SZ, and areas with the tunnel window is made in the same process memory cells "fast" EPROM, both memory cells have the same properties of programming/erasing.

2. The method according to p. 1, wherein performing the tunneling region (TG) is performed with MD-implantation.

3. The method according to p. 1, wherein performing the tunneling region (TG) is performed with LDD-implantation.